Truncheon

Then he stumbled over a corpse, and a bludgeon knocked the dented helmet from his head; the next instant the club fell full on his unprotected skull. - The Hour of the Dragon

Used by watchmen and criminals alike, the truncheon is designed for incapacitating enemies without killing them.

Shemitish slavers have been known to waylay travelers leaving taverns in the meadowland cities and expertly knocking them out. The poor wretches awaken the next day in a wagonful of other captives with sore heads, on their way to the slave markets of the east.

It takes a great deal of experimentation to understand how to hit an enemy just hard enough to knock them out without smashing their skull.